Filter



I. Feb. 13, 1940. at. LOFGREN FILTER Filed Sept. 2, 1937 INVENTOR.

4,; ATTORNEY.

Patented Feb. 13, 1940 UNITED STATES PATENT OFFICE m'mn". Gustaf Einar Loi'gren, Riverside, 061111.. assignor to Electrolux poration of Delaware Corporati on, Dover, DeL, a cor- Application September 2, 1937, Serial.No. 162,103

My invention relates to filters and I ticularly to a filter for use with vacuum cleaners.

An object of my invention is to provide an improved filter for use with vacuum cleaners,

providing a relatively large area for efficiently removing the dirt from the air and without, at the same time, producing a large back pressure.

What I consider to be novel and my invention may be better understood by reference to the following specification and appended claims when considered in connection with the accompanying drawing, in which Fig. 1 is a side view of a vacuum cleaner broken normal use as a suction cleaner, dirt ladened air enters through opening II and most of the dirt carried thereby is deposited in a bag, not shown. There may be fine particles of dust which are not separated from the air by the bag and to prevent this fine dust from passing out the outlet opening l2 into the atmosphere and also to catch any carbon dust from the motor brushes, a filter I3 is provided and located adjacent the opening I2. As better indicated in Figs. 2 and 3, a metal frame I4 is provided substantially of cylindrical form or cup shape with a depression I5 formed at one end by inwardly projecting arms I B integral with the body of frame l4. Projecting from the opposite end of frame I4 are fingers I! with inwardly extending radial projections I8. These fingers I! are adapted to secure the filter i3 to a. housing l9 located adjacent the opening I 2. by means of the projections i8 which snap into an annular recess 20 in the housing I9. A shoulder 2! of the frame l4 adjacent the fingers II serves as a stop in the mounting of filter I3 on housing I9. The frame I4 is cut away at its end and sides to present a minimum of obstructing surface to the passage of air, at the same time providing a. substantially rigid construction.

The shape of the frame It with its cylindrical form or cup "shape having considerable depth,

presents a much larger filtering area than the more par 4 Claims. (c1. far-+49) V conventional disc shapedfiltcrs. Any desired cross-sectional shapecan be used with a corresponding depth to provide the required filtering area. With a largearea, a greater amount of air can be passed through the filterflwith a lesser drop in pressure or, in other words, a lower back pressure than would be produced by filtering with a smaller area.

To filter the'dust from the air, filtering material consisting of two layers of fabric 22 and 23 are located around the frame I4 as best indicated in Fig. 1. The layer of fabric 22 consisting of a plurality of layers 24 of felted fibers, such as cotton, backed by a cloth. 25 of coarse weave is. formed in a rectangular shape and wound around the cylindrical part of frame ll,

spaced a short distance from the open'end portion of the periphery of the frame. The cloth 25, in addition to serving as a backing for the layers 24 of fibers, due to its location on the inside of fabric 22 prevents the fibers from being carried out with the air through outlet opening I2. Prior to the application of fabric 22, frame I is covered with a sticky substance for securing the fabric to the frame. The portion or excess of the fabric 22 extending beyond the end or the cylindric height-of the frame H is loosely tucked in the depression or recess ii of the frame I as' best indicated in Fig. 6. It may be desirable in some cases to pre-form the fabric 22 with a folded end and then secure it to the frame II.

However, it is more economical as a manufacturing process to wind a fabric of rectangular shape around the frame securing it at one end and then folding the free end of the fabric around the opposite end of the frame. The folded end of the fabric 22 provides a plurality of layers of fabric through which the air passes. Each layer of fabric 22 consists of a plurality of layers 24 of fibers and a layer of cloth 25. Each one of these layers provides a surface on which dust may be deposited. A single layer would soon be clogged with dust that could easily be deposited on these plurality of layers of material without interfering with the passage of air therethrough. Either fabric 22 or fabric 23, or both, may be impregmated with a substance for purifying the air as it passes through it. The fabric 23 is formed in a shape conforming substantially to the shape of the frame I4. It is secured to the frame ll by means of a sticky or gummy substance placed on loosen up or unfold in the depression l6 of the frame M which would reduce its effectiveness as a filter by permitting air to flow between its folds, is prevented by the covering 23. Covering also 'serves as an additional layer of material upon which dust may be deposited as the air passes through. filter l3.

When the member of layers of material comprising a filter element is increased the resistance a to the flow of air therethrough is increased but this increase in resistance may be offset by an increase in the filter area. Thus, by providing a filter having a considerable depth, a plurality of layers of filtering material may be used to increase the efficiency of the filter without increasing the resistance to the fiow of air. In addition, theplurality of layers of filtering material act as a sound deadening material and j reduces theamount of noise that passes through the filter. a In this manner less of the noise produced by the & proved filter is provided presenting a relatively large area with many layers of filtering material, which is of relatively simple construction and may be economically manufactured.

What I claim is:

l. A filter comprising a frame of substantially cylindrical form having a depression at one end,

a covering of fabric of a length to extend beyond the cylindric height of said frame, said covering being secured around the periphery of said frame and the excess length ofv said fabric being loosely v folded in said depression, and an outer covering of frabric secured to said frame and enclosing said first-named covering.

2. A filter comprising a frame of cup shape having openings in its sides and ends, a covering of fabric for said side openings of a length to extend beyond the end of said frame, said cover being loosely folded over one end, and an outer covering of fabric secured to said frame and enclosing said first-named covering.

3. A filter comprising a frame of substantially cylindrical form having inwardly extending arms at one end forming a concave recess, fingers formed integrally with said frame extending from the end opposite said last-named end and having inwardly extending projections, a covering of fabric of a length to extend beyond the cylindrlc height of said frame, said covering being secured I V around the periphery of said frame and being,

loosely folded in said recess, and an outer covering of fabric secured to said frame and inclosing said-- first-named coverings, said fingers being adapted to secure said frame to a support.

4. A filter comprising a box-like frame, a plurality of layers of fibers backed by cloth of a length to extend beyond one end of said frame, said cloth being secured to the outer periphery of one end of said frame and the excess length of said cloth being loosely folded over the other end of said frame, and a second covering of fabric secured to said frame.

GUSTAF EINAR LOFGREN. 

